Muhammad Ibn Abd al-Wahhab (1703–92) remains a controversial figure, a fact exemplified by the title of Charles Allen’s 2006 book on Wahhabism, God’s Terrorists: The Wahhabi Cult and the Hidden Roots of Modern Jihad. This new biography by Michael Crawford, a former senior British civil servant specialising in the Arab world, is accurate, dry but at the same time fascinating. It may not tell us much about the man, for his biographical details are sparse, but it does explain what was so compelling about the austere creed he conceived, and how the Al Saud clan exploited it to expand their hegemony over the Two Holy Places and what eventually became Saudi Arabia. In recent decades, the Saud dynasty has used its enormous oil wealth to spread the Wahhabist version of Islam far and wide, though it is often not in control of how it is locally interpreted. Crawford’s achievement is a very limpid and precise book, and a surprising one in many places.